Production Process I
Introduction
A. Syllabus, paper pattern
Introduction
B. Introduction to the subject
Introduction
B. Introduction to the subject
1. What is manufacturing?
Introduction
C. Classification of manufacturing processes
Solidification Process
Particulate Process
Deformation Process
Material removal Process
Module I
Metal casting process
Metal Casting Process
A. Fundamental of metal casting
1. Casting
2. Mold
3. Pattern
Open Mold
Closed Mold
Casting is a process in which the molten metal flows by gravity or forced into a
mold, where it solidifies and finally after cooling, it acquires the shape of the mold
cavity.
Metal Casting Process
2. Mold
Depending upon the extraction of cast product, the
casting process in divided into
Expendable mold - casting process
•Sand mold casting
•Shell mold casting
•Vacuum mold casting
•Investment casting
•Carbon dioxide mold casting
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
Permanent mold - casting process
•Die casting
•Centrifugal casting
Metal Casting Process
2. Mold
2.1 Mold materials
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
Sand Casting Process
A. Fundamental of sand casting
1. Casting
2. Mold
3. Pattern
Casting Terms :
•Mold: It contains a cavity whose geometry determines the shape of the cast part.
•Cope: It is the upper half of the mold.
•Drag: It is the bottom half of the mold.
•Flask: A metal or wood frame, without fixed top or bottom, in which the mold is
formed.
Sand Casting Process
A. Fundamental of sand casting
1. Casting
2. Mold
3. Pattern
•Parting line: This is the dividing line between the two molding flasks that makes up
the mold.
•Pattern: It is the replica of the final object to be made. The mold cavity is made with
the help of pattern.
•Molding sand: Sand, which binds strongly without losing its permeability to air or
gases. It is a mixture of silica sand, clay, and moisture in appropriate proportions.
Sand Casting Process
A. Fundamental of sand casting
1. Casting
2. Mold
3. Pattern
•Facing sand: The small amount of carbonaceous material sprinkled on the inner
surface of the mold cavity to give a better surface finish to the castings.
•Core: A separate part of the mold, made of sand and generally baked, which is
used to create openings and various shaped cavities in the castings.
•Chaplets: Chaplets are used to support the cores inside the mold cavity to take
care of its own weight.
Sand Casting Process
A. Fundamental of sand casting
1. Casting
2. Mold
3. Pattern
•Pouring basin: A small funnel shaped cavity at the top of the mold into which the
molten metal is poured.
•Sprue: The passage through which the molten metal, from the pouring basin,
reaches the mold cavity.
•Runner: The channel through which the molten metal is carried from the sprue to
the gate.
•Gate: is that portion of runner through which the molten metal enters the mold cavity.
Sand Casting Process
1. Fundamental of sand casting
1. Casting
2. Mold
3. Pattern
•Riser: it serves as reservoirs to supply the molten metal necessary to prevent
shrinkage during solidification.
•Vent: Small opening in the mold to facilitate escape of air and gases.
Metal Casting Process
2.2 Constituent of Molding Sand
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
The main constituents of molding sand involve silica sand, binder, moisture content
and additives.
Silica sand (88%-92%)
•Silica sand form the main constituent of molding sand having enough refractoriness
which can impart strength, stability and permeability to molding and core sand.
•The silica sand can be specified according to the size (small, medium and large silica sand
grain) and the shape (angular, sub-angular and rounded).
•But along with silica small amounts of iron oxide, alumina, lime stone, magnesia, soda and
potash are present as impurities.
Metal Casting Process
2.2 Constituent of Molding Sand
Binder (6%-12%)
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
•In general, the binders can be either inorganic or organic substance.
•The inorganic group includes clay, sodium silicate etc.
•In foundry shop, the clay acts as binder which may be Ball Clay, Fire Clay, Limonite, Fuller’s
earth and Bentonite.
•Organic group binders are dextrin, molasses, cereal binders, linseed oil and resins like phenol
formaldehyde, urea formaldehyde etc.
•Among all the above binders, the bentonite variety of clay is the most common.
Metal Casting Process
2.2 Constituent of Molding Sand
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
Moisture (3%-6%)
•The effect of clay and water decreases permeability with increasing clay and moisture
content.
•The green compressive strength first increases with the increase in clay content, but after a
certain value, it starts decreasing.
Metal Casting Process
2.2 Constituent of Molding Sand
Additives
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
Some common used additives for enhancing the properties of molding and core sands
are discussed as under.
•Coal dust
•Corn flour
•Dextrin
•Sea coal
•Pitch
•Wood flour
•Silica flour
Metal Casting Process
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
2.3 Kinds of Molding Sand
•Green sand
•Dry sand
•Loam sand
•Facing sand
•Backing sand
•System sand
•Parting sand
•Core sand
Metal Casting Process
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
2.4 Properties of Molding Sand
•Refractoriness
•Permeability
•Green Strength
•Dry Strength
•Collapsibility
•Cohesiveness
• Reusability
Metal Casting Process
2.5 Steps involved in making Sand Mold
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
•The first step in making mold is to place the pattern on the molding board.
•The drag is placed on the board
•Dry facing sand is sprinkled over the board and pattern to provide a non sticky layer.
•Molding sand is then riddled in to cover the pattern with the fingers; then the drag is
completely filled.
•The sand is then firmly packed in the drag by means of hand rammers. The ramming must
be proper i.e. it must neither be too hard or soft.
•After the ramming is over, the excess sand is leveled off with a straight bar known as a strike
rod.
•With the help of vent rod, vent holes are made in the drag to the full depth of the flask as well
as to the pattern to facilitate the removal of gases during pouring and solidification.
Metal Casting Process
2.5 Steps involved in making Sand Mold
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
•The finished drag flask is now rolled over to the bottom board exposing the pattern.
•Cope of the pattern is then placed over the drag pattern with the help of locating pins.
•The dry parting sand is sprinkled all over the drag and on the pattern.
•A sprue pin for making the sprue passage is located at a small distance from the pattern.
Also, riser pin, if required, is placed at an appropriate place.
•The operation of filling, ramming and venting of the cope proceed in the same manner as
performed in the drag.
•The sprue and riser pins are removed first and a pouring basin is scooped out at the top to
pour the liquid metal.
Metal Casting Process
2.5 Steps involved in making Sand Mold
1. Casting
2. Mold
2.1 Mold materials
2.2 Constituent of Molding Sand
2.3 Kinds of Molding Sand
2.4 Properties of Molding Sand
2.5 Steps involved in making Sand Mold
2.6 Venting of Molds
3. Pattern
•Then pattern from the cope and drag is removed and facing sand in the form of
paste is applied all over the mold cavity and runners which would give the
finished casting a good surface finish.
•The mold is now assembled. The mold now is
ready for pouring
Metal Casting Process
3. Pattern
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
Pattern is the replica of the final object to be made by the casting process, with
some modifications.
The main modifications are the addition of pattern allowances . If the casting is to be
hollow, additional patterns called cores are used to create these cavities in the
finished product.
The quality of the casting produced depends upon the material of the pattern, its
design, and construction.
Metal Casting Process
3.1. Objectives of the Pattern
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
•A pattern prepares a mold cavity for the purpose of making a casting..
•Runner, gates, and risers used for feeding molten metal in the mold cavity may form a
part of the pattern.
•Patterns properly made and having finished and smooth surfaces reduce casting
defects.
•A properly constructed pattern minimizes the overall cost of the castings.
Metal Casting Process
3.2. Types of Pattern
•Single piece/solid pattern
•Two piece/split pattern
•Multi piece pattern
•Cope & drag pattern
•Loose piece pattern
•Match plate pattern
•Follow board pattern
•Gated pattern
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
Metal Casting Process
3.2. Types of Pattern
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
Metal Casting Process
3.2. Types of Pattern
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
Metal Casting Process
3.3. Pattern material
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
Some materials used for making patterns are:
• Wood
•Metals and alloys like cast iron, brass & bronze, Aluminium alloys
•Plaster of Paris,
• Plastic and rubbers,
•Wax, and resins.
Metal Casting Process
3.3. Pattern material
To be suitable for use, the pattern material should be:
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
•Easily worked, shaped and joined
•Light in weight
•Strong, hard and durable
•Resistant to wear and abrasion
•Resistant to corrosion, and to chemical reactions
•Dimensionally stable and unaffected by variations in temperature and humidity
•Available at low cost
Metal Casting Process
3.4. Pattern Allowance
•Shrinkage or contraction allowance
Liquid Shrinkage & Solid Shrinkage
•Draft or taper allowance
Positive allowance of 10mm to 20mm/m
•Machining or finish allowance
Positive allowance of 3mm to 18mm
•Distortion allowance
•Rapping allowance
Negative allowance of 0.5mm to 1mm
1. Casting
2. Mold
3. Pattern
3.1. Objective of pattern
3.2. Type of pattern
3.3 Common pattern materials
3.4. Pattern Allowance
RISER
Considerations for Designing Riser
(A) Freezing time
(B) Feeding range
(C) Feed Volume Capacity
SOLIDIFICATION TIME
Chvorinov’s Rule
Chvorinov’s rule indicates that a casting with a higher volume-to-surface area ratio
will cool and solidify more slowly than one with a lower ratio.
CASTING DEFECTS
Metal Casting Process
1. Casting
2. Mold & its types
3. Patterns
3. Advantages and disadvantages
Advantages:
The metal casting process is extensively used in manufacturing because of its many
advantages.
1.Molten material can flow into very small sections so that complicated shapes can be made by
this process. As a result, many other operations, such as machining, forging, and welding, can
be minimized or eliminated.
2.It is possible to cast practically any material that is ferrous or non-ferrous.
3.As the metal can be placed exactly where it is required, large saving in weight can be
achieved.
4.The necessary tools required for casting molds are very simple and inexpensive. As a result,
for production of a small lot, it is the ideal process.
5.There are certain parts made from metals and alloys that can only be processed this way.
6.Size and weight of the product is not a limitation for the casting process.
Metal Casting Process
A. Fundamental of metal casting
1. Casting
2. Mold & its types
3. Advantages and disadvantages
Limitations:
1.Dimensional accuracy and surface finish of the castings made by sand casting processes
are a limitation to this technique. Many new casting processes have been developed which
can take into consideration the aspects of dimensional accuracy and surface finish. Some of
these processes are die casting process, investment casting process, vacuum-sealed molding
process, and shell molding process.
2.The metal casting process is a labor intensive process
Shell mold casting
Vacuum mold casting
Investment casting
Permanent mold casting
The basic permanent-mold process
DIE CASTING - Hot chamber die casting
DIE CASTING - Cold chamber die casting
Centrifugal casting